Combination vaccines (which provide protection against multiple pathogens) are very desirable in order to minimise the number of immunisations required to confer protection against multiple pathogens, to lower administration costs, and to increase acceptance and coverage rates. The well-documented phenomenon of antigenic competition (or interference) complicates the development of multi-component vaccines. Antigenic interference refers to the observation that administering multiple antigens often results in a diminished response to certain antigens relative to the immune response observed when such antigens are administered individually.
Combination vaccines are known which can prevent Bordetella pertussis, Clostridium tetani, Corynebacterium diphtheriae, and optionally inactivated poliovirus (IPV), and/or Hepatitis B virus, and/or Haemophilus type B infection (see for instance WO 93/24148, WO97/00697 and WO2000/030678).
After many years of research the standard dose of polio vaccines accepted as effective within the vaccine community today contains 40 D antigen units of inactivated poliovirus type 1(Mahoney), 8 D antigen units of inactivated poliovirus type 2(MEF-1) and 32D antigen units of inactivated poliovirus type 3(Saukett) (e.g. INFANRIX-IPV™).
The present inventors have surprisingly found that reduced doses of IPV can maintain an adequate or improved level of protection against polio. Such vaccines carry considerable advantages including the ability to provide more doses of IPV vaccines for the individuals in need thereof.